Polydisilazane resins are precursors to silicon carbide and silicon nitride fibers and coatings. These resins must be formulated such that they may be processed into the desired shape (for instance, a fiber), while being stable enough to allow resin storage, hot melt spinning, cure and post-spinning handling processes without significant change in composition
The chlorine content in a polydisilazane resin, such as that obtained by a process described in US 2011/0212329 (Pope et al.), is typically above 1 wt %. The resulting resin has low stability both in solution and during the melt spinning process to make fibers. These high halogen resins will react with moisture and hydrolyze, resulting in an unstable fiber spinning process or coating application and substantial incorporation of oxygen. Because of this, the presence of high halogen content requires that the spinning and other steps cannot be performed in an open atmosphere.
Various methods have been used to attempt to reduce halogen concentration in polysilazane resins. Many of these methods, such as that shown in U.S. Pat. No. 5,200,371 (Takeda et al.), utilize chemicals that are toxic to workers, such as ammonia. Such processes present several environmental health and safety challenges and are expensive due to the toxic nature of the reagents.
Therefore, a non-toxic, cost-effective process is needed for the production of polysilazane resins.